A method specifically used to predict the glycemic index of rice

Abstract

The present invention discloses a method for predicting the glycemic index of rice, and belongs to the technical field of food detection. The present invention develops an in vitro digestion model dedicated to rice, thereby obtaining in vitro digestion test parameters, using rice with known GI as a standard reference, establishing a mathematical function association between the in vivo GI index and the in vitro simulated digestion parameters, and realizing accurate prediction of the GI index of the rice to be tested, and its linear correlation r is above 0.95, and the prediction accuracy is high. The present invention reduces unreasonable or unnecessary steps in the traditional method of in vitro determination of the glycemic index of rice, and the operation is simpler. The present invention can also be applied in rice variety screening and rice breeding. At present, there is no unified method dedicated to predicting the in vitro rapid detection of rice GI value, which is original.

Description

Technical Field

[0001] The invention relates to a method specially used for predicting the glycemic index of rice, belonging to the technical field of food detection. Background Art

[0002] Rice (Oryza sativa L.) is mainly composed of starch, protein and lipids, and is one of the important staple foods for more than half of the world's population. Among them, starch is the main carbohydrate in rice, and its digestion behavior is the key to affecting blood sugar response. Due to its easy digestion and absorption, eating rice will cause blood sugar to rise rapidly. Therefore, rice is often considered a food with a high glycemic index (GI). In recent years, the public's health awareness has been increasing, and consumers' demand for dietary nutritional quality has gradually increased. With the development of agronomy and breeding, medium and low GI varieties of rice have also emerged.

[0003] Human trials are the most important method for determining GI, and are also the standard method for determining food GI at home and abroad. They are mainly based on the concept of GI, and measure the changes in blood sugar after a person eats a food containing 50g of carbohydrates. The method of determining GI in human trials is affected by multiple factors, including the physical health of the subjects, the number of subjects, pre-test meal, exercise and drug requirements, reference food, effective CHO in the tested food, the frequency in the test procedure, glucose monitoring methods and data processing. In addition, this method of testing GI in human experiments is labor- and time-intensive, requiring the recruitment and screening of human subjects, which results in high economic and time costs. Reference and test foods must be consumed on different dates, and it usually takes several days to complete the test. In addition, due to the large amount of samples consumed in human experiments, newly bred rice samples often cannot meet the needs of human experiments. In summary, due to the high price, long time consumption, large sample demand, and high personnel requirements of human GI, there are great limitations for the development and testing of healthy foods in the food industry.

[0004] Therefore, due to the advantages of in vitro simulated digestion methods such as fast, good repeatability and low cost, they are increasingly used to predict and compare the GI of food. At present, the methods for determining rice GI under in vitro conditions are mainly the methods of Englyst and M.Minekus. The principle is to use enzymes to hydrolyze starch and calculate the amount of hydrolyzed starch by measuring the amount of glucose released. The first type of method is relatively simple. Food is enzymatically hydrolyzed in a fixed buffer. Many existing methods are modified with reference to the Englyst method. However, due to the great differences between different experimental methods, the results between different research groups are not comparable. In addition, this type of method does not take into account multiple digestion stages and multiple non-starch components, which has great limitations. The second type of M.Minekus method has starch digestion stages simulating the oral, gastric and small intestinal stages. The buffer preparation is extremely complex, involving salivary amylase, pepsin, trypsin, pancreatic amylase, convertase, bile salts and other enzymes, and for different foods, the enzyme types and concentrations are too diverse. As a potential healthy staple food, low GI rice is particularly important to invent a method specifically for predicting the glycemic index of rice.

[0005] In summary, in the field of in vitro test prediction of rice GI, many existing analytical methods have significant defects, which can be simply summarized as follows: (1) There is no unified method for predicting rice GI value in vitro; As shown above, the current in vitro simulated digestion methods do not take into account the differences in digestion characteristics between different carbohydrate foods; In fact, the inventors of the present invention also found that these methods predict rice foods indiscriminately, and even cannot distinguish low GI rice from high GI rice, that is, the rice GI value predicted by the existing model is not accurate enough; (2) Unreasonable or unnecessary simulated digestion steps lead to cumbersome operations. At present, most in vitro digestion test methods are based on simulating digestion in the mouth, stomach and small intestine; In fact, the inventors also found that for some food samples, simulating digestion in the human mouth or stomach is not necessary, and should be adjusted according to actual conditions to further streamline the existing in vitro digestion model.

[0006] Therefore, the development of a relatively simple method for predicting the glycemic index of rice can not only be used for the screening of low GI rice varieties, but also for the development of new rice product products. Summary of the invention

[0007] In view of the fact that the in vitro digestion model methods of different kinds of food vary greatly, the results obtained by different methods are not comparable, the rice GI value predicted by the existing model is not accurate enough, and the existing prediction model is not simple enough, the present method aims to invent an in vitro digestion model specifically for rice and use it specifically for predicting the glycemic index of rice. The method of the present invention is efficient, simple, accurate, and can specifically measure the GI value of rice.

[0008] The method for predicting the glycemic index of rice provided by the present invention comprises: performing in vitro digestion simulation on the rice to be predicted, obtaining the in vitro digestion parameter AUC-60, and then substituting the AUC-60 value as x into a model y=0.0548x-134.42 to obtain a y value, wherein the y value is the glycemic index (GI value) of the rice.

[0009] In one embodiment, the in vitro digestion parameter AUC-60 refers to measuring the reducing sugar release at multiple time points within 0-60 minutes after the start of the enzymatic digestion reaction of the rice to be tested in vitro simulating the human small intestine, making a reducing sugar release curve, and converting it into a digestion curve with starch digestibility as the vertical axis (value range 0-100) and reaction time (unit min) as the horizontal axis; performing definite integral calculation to obtain the area under the in vitro digestion curve of the rice to be tested within 0-60 minutes, which is the in vitro digestion parameter AUC-60.

[0010] In one embodiment, the in vitro digestion simulation of the predicted rice comprises:

[0011] (4) simulating rice cooking to obtain a rice mixture;

[0012] (5) In vitro simulation of human stomach enzymatic digestion reaction activity:

[0013] After cooling the mixed solution obtained in step (1), reacting it with simulated gastric digestive juice to simulate the gastric digestion process of rice in the human body, and terminating the gastric digestion process after reaching the time;

[0014] (6) In vitro simulation of enzymatic digestion reaction activities of the human small intestine:

[0015] The mixed solution obtained in step (2) is reacted with simulated small intestinal digestive fluid to simulate the intestinal digestion process of rice in the human body.

[0016] In one embodiment, the method for simulating rice cooking in step (1) comprises the following steps: adding rice grains into a glass bottle, wherein the rice varieties to be measured are required to be consistent, the grains have a complete appearance, and there are as few gaps as possible; adding 3-6 mL of deionized water for every 100-300 mg of rice grains; and boiling the rice grains while avoiding destroying the complete grain structure of the rice or causing the rice to stick to the wall.

[0017] In one embodiment, the in vitro simulation of the enzymatic digestion reaction activity of the human stomach in step (2) comprises the following steps: preparing simulated gastric juice with a pH of 2.0, wherein the simulated gastric juice contains a hydrochloric acid concentration of 0.02M-0.03M and a pepsin concentration of 2000-3000U / ml; activating the simulated gastric juice by water bath to obtain an activated digestive juice, wherein the temperature of the activated water bath is 37°C, the time is 10-20min, and the rotation speed is 200rpm-400rpm; then adding the activated digestive juice to the rice of step (1), performing simulated gastric digestion at a rotation speed of 100-200rpm for 30min, and then terminating the gastric digestion.

[0018] In one embodiment, in step (2), the gastric digestion process is terminated by adding NaOH to change the pH; the concentration of the NaOH solution is 0.02M-0.03M; and the digestion termination time is 5-10min.

[0019] In one embodiment, the in vitro simulated human small intestine enzymatic digestion reaction activity of step (3) is performed using activated simulated small intestinal digestive fluid at 37°C and 100-200 rpm for 3 hours; wherein the simulated small intestinal digestive fluid contains sodium acetate buffer and digestive enzymes.

[0020] In one embodiment, the sodium acetate buffer has a concentration of 0.2M, which is prepared by dilution of 2M sodium acetate and 0.2M acetic acid, with a pH of 6.0; it also contains 1-5mM CaC12 and 0.2-1mM MgC12; the digestive enzymes are composed of pancreatic α-amylase and glucoside amylase, wherein the concentration of pancreatic α-amylase is 1-20U / ml, and the concentration of glucoside amylase is 1-10U / ml; the activated simulated small intestinal digestive fluid refers to treating the simulated small intestinal digestive fluid at 37°C and 200rpm-400rpm for 10-20min.

[0021] In one embodiment, the concentration of the glucoside amylase is 10 U / ml.

[0022] In one embodiment, the in vitro digestion parameters are obtained by fitting the digestion curve based on a mathematical model to obtain the in vitro digestion test parameters; specifically, a reducing sugar release curve is prepared according to the reducing sugar concentration released at each reaction time point during in vitro enzymatic digestion, and the reducing sugar release curve is converted into a digestion curve consisting of starch digestion percentage and reaction time; the area under the in vitro digestion curve of the rice to be tested is obtained by definite integral calculation, which is the in vitro digestion parameter.

[0023] In one embodiment, the model is constructed by conducting an in vitro digestion simulation experiment on a standard carbohydrate food standard (rice) with a known GI value, and establishing a functional relationship between the glycemic index GI of the standard sample and the in vitro digestion parameter AUC-60.

[0024] In one embodiment, the method for determining the reducing sugar content comprises the following steps:

[0025] At a specific time point, the supernatant is aspirated to terminate the simulated intestinal digestion of rice by the human body, and a sample solution to be tested is obtained;

[0026] The sample solution to be tested is mixed with the GOPOD reagent in a 96-well plate and incubated, and the absorbance value is detected. The reducing sugar content is calculated based on the absorbance value of the standard glucose solution concentration.

[0027] In one embodiment, in the method for determining the reducing sugar content, each time point refers to the stage of enzyme digestion reaction simulating the human small intestine, 0, 10, 20, 30, 60, 90, 120, 180 minutes after adding the enzyme solution.

[0028] In one embodiment, in the method for determining the reducing sugar content, the reagent for terminating the simulated intestinal digestion process of rice by the human body is anhydrous ethanol; optionally, the volume ratio of the sample liquid to the anhydrous ethanol is 1:4-9.

[0029] In one embodiment, in the method for determining the reducing sugar content, the sample solution and the GOPOD reagent are calculated at a volume ratio of 1:20-40; optionally, the incubation time is 10-20 min, the incubation temperature is 35-45° C., and the determination condition is absorbance at 510 nm.

[0030] The invention also provides application of the method in rice variety screening and rice breeding.

[0031] Advantages and effects of the present invention:

[0032] (1) The present invention develops a prediction method specifically for the glycemic index of rice, which is more targeted, more accurate and more repeatable. The prediction method of the present invention uses rice with known GI as a standard reference, establishes a mathematical function association between the in vivo GI index and the in vitro simulated digestion parameters, and realizes the accurate prediction of the GI index of the rice to be measured. The linear correlation r is above 0.95, and the prediction accuracy is higher.

[0033] (2) The present invention reduces the unreasonable or unnecessary steps in the traditional method of in vitro determination of the glycemic index of rice, and the operation is simpler. At the same time, it overcomes the defect of the traditional technology that the isolated point test cannot reflect the overall digestion situation.

[0034] (3) The method for determining the glycemic index of rice in vitro of the present invention does not overly rely on professional statistical software for data analysis, which greatly reduces the time for data analysis, and the accuracy of the data can be fully guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The in vitro digestion curves of 8 different rice varieties with known GI values.

[0036] Figure 2 This is a graph showing the relationship between the GI values ​​of rice varieties with known GI values ​​in Example 1 and their in vitro digestion parameters.

[0037] Figure 3 The effects of different in vitro digestion model combinations on the in vitro digestion curve of starch of Doongara rice.

[0038] Figure 4 This is the relationship between the GI value of the rice variety with known GI value in Comparative Example 2 and the predicted GI value.

[0039] Figure 5 This is the in vitro digestion curve of rice in Comparative Example 2.

[0040] Figure 6 This is the prediction model constructed after changing the concentration of glucoside amylase in Comparative Example 3. DETAILED DESCRIPTION

[0041] Commercial rice with known GI values ​​was selected, among which Jasime, Doongara, and Akita Komachi rice were purchased from Australia Sunrice Company; JK rice was purchased from Jiangnan Rice Road Jiangsu Technology Co., Ltd.; NJ46, NJ9108, and WYG rice were purchased from Jiangsu Agricultural Reclamation Agricultural Development Co., Ltd.; TRF rice was purchased from Anhui Sugar and Lipid Steward Technology Co., Ltd.; GQ rice was purchased from Zhejiang Wanxinglai Rice Industry Co., Ltd.; WT rice was purchased from Chengdu Tianjianjun Technology Co., Ltd.; ST rice was purchased from Tunkmai Biotechnology Research Co., Ltd. Among them, Jasime, Akita Komachi, WYG, NJ46, Doongara, JK, GQ, and WT are 8 kinds of rice that have been clinically tested and have clear clinical GI values. Their clinical GI values ​​are shown in Table 1 below, as standard rice foods. TRF, NJ9108, and ST are used as rice foods to be tested.

[0042] Example 1: Establishment of a method specifically for predicting the glycemic index of rice

[0043] Table 1 GI values ​​of different rice varieties

[0044]

[0045] A method for predicting the glycemic index of rice, comprising the following steps:

[0046] (1) In vitro test simulating rice cooking:

[0047] Weigh 200±10mg of intact rice grains and add them into the reagent bottle;

[0048] Add 2.0 mL of distilled water to the reagent bottle and tighten the cap;

[0049] The mixture was heated in a water bath at 100°C with stirring for 30 min to obtain a simulated cooking sample.

[0050] (2) In vitro tests simulate gastric digestion process:

[0051] 4.0 mL of simulated gastric fluid was added to a reagent bottle, and stirred in a 37°C water bath with a magnetic rotor at 200 rpm for 30 min to obtain simulated gastric digestion; wherein the simulated gastric fluid had a pH of 2.0, contained 0.03 M hydrochloric acid, and contained 2000 U / ml pepsin; the simulated gastric fluid was activated by water bath to obtain activated digestion fluid, wherein the temperature of the activated water bath was 37°C, the time was 20 min, and the rotation speed was 400 rpm;

[0052] When the digestion was terminated, 4.0 mL of NaOH solution was added and reacted for 10 min to obtain a simulated gastric digestion sample.

[0053] (3) In vitro tests simulate intestinal digestion process:

[0054] 10.0 mL of simulated small intestinal digestive fluid was added to a reagent bottle, and stirred at 200 rpm in a 37°C water bath for 180 min to simulate the intestinal digestion process of carbohydrate food in the human body to obtain an intestinal digestion simulator. The simulated small intestinal digestive fluid contained sodium acetate buffer and digestive enzymes; the sodium acetate buffer had a concentration of 0.2 M, and was prepared by diluting 2 M sodium acetate and 0.2 M acetic acid, pH 6.0, and also contained 5 mM CaC12 and 1 mM MgC12; the digestive enzymes consisted of pancreatic α-amylase and glucoside amylase, wherein the concentration of pancreatic α-amylase was 20 U / ml, and the concentration of glucoside amylase was 10 U / ml; the simulated small intestinal digestive fluid was activated by water bath to obtain activated digestive fluid, wherein the temperature during the activation water bath was 37°C, the time was 20 min, and the speed was 400 rpm.

[0055] After the simulated small intestinal digestion stage begins, take the supernatant at 0, 10 min, 20 min, 30 min, 60 min, 90 min, 120 min, and 180 min, respectively. Take 200 μL of the sample each time and quickly transfer the sample to a 2 mL centrifuge tube with a cap to which 800 μL of anhydrous ethanol has been added in advance. Quickly close the cap and shake to inactivate the enzyme to serve as the test sample solution.

[0056] (4) Digestion product test:

[0057] a. Centrifuge the sample solution to be tested, take 10 μL of the supernatant and add it to a 96-well plate, with 2 parallels for each sample;

[0058] b. Prepare a standard glucose solution with a concentration range of 0.2-1 mg / mL containing 0.2% w / v sodium azide, take 10 μL of the supernatant and add it to a 96-well plate, with 2 replicates for each sample;

[0059] c. Take 200 μL of GOPOD solution (purchased from Megazyme) and add it to a 96-well plate. Incubate at 37°C with shaking for 15 minutes and measure its absorbance at 510 nm. Based on the linear relationship between the concentration of the standard glucose solution and the absorbance, the amount of reducing sugar released by the rice under the simulated digestion reaction in vitro at each time point can be obtained;

[0060] (5) Fit the digestion curve based on the mathematical model to obtain the in vitro digestion test parameters:

[0061] a. Based on the reducing sugar concentration released by in vitro enzymatic digestion at each reaction time point, a reducing sugar release curve was prepared and converted into a digestion curve consisting of starch digestion percentage and reaction time; wherein, using 8 different rice varieties with known GI values ​​in Table 1, the digestion curve consisting of starch digestion percentage and reaction time obtained by the above method is as follows: Figure 2 As shown;

[0062] b. Conduct in vitro digestion experiments on standard carbohydrate food standards with known GI values ​​to clarify and establish the functional relationship between the glycemic index GI of standard samples and in vitro digestion parameters;

[0063] The in vitro digestion curves of starch of 8 kinds of rice in Table 1 ( Figure 1 ) were subjected to the same fitting process, and the definite integral was calculated within 0-60 min to obtain the area under the in vitro digestion curve of each rice, i.e., the AUC-60 value. For the above 8 rice varieties with known GI values, the functional relationship between the glycemic index GI value of the rice sample and AUC-60 was established, y=0.0548x-134.42, where GI value is y and AUC-60 is x. The results are as follows Figure 2 .

[0064] like Figure 2 As shown in Figure 2, for 8 rice standards, AUC-60 as a key in vitro digestion parameter showed a linear relationship with the GI value, and R 2 =0.9594. This indicates that the relationship between the in vitro digestion parameters obtained by the method of the present invention and the GI value is linearly correlated above 0.95, and the prediction accuracy is higher.

[0065] Example 2: Application of a method specifically for predicting the glycemic index of rice

[0066] For the rice whose GI value is to be measured, the rice to be predicted is subjected to in vitro digestion simulation with reference to the method of Example 1. In the simulated small intestinal digestion stage, a reducing sugar release curve is prepared according to the reducing sugar release amount in different time periods within 0-60 min, and it is converted into a digestion curve consisting of starch digestion percentage and reaction time, and the area under the in vitro digestion curve AUC-60 at 60 min is obtained, that is, x, and then x is substituted into the model y=0.0548x-134.42 to obtain the y value, which is the predicted rice glycemic index. Specifically, according to the in vitro digestion parameters of the rice to be measured, the glycemic index of the sample to be measured, that is, the predicted GI value, is predicted by comparing the functional relationship between the GI value of the standard product established in Example 1 and its in vitro digestion test parameters.

[0067] As shown in Table 2, the predicted GI values ​​and clinical GI values ​​of multiple samples were compared. The results showed that the error between the GI value determined by the method of the present invention and the GI value obtained by human experiments was within 4%, indicating that the method of the present invention is accurate and reliable.

[0068] Table 2 AUC-60 and predicted GI values ​​of rice digestibility parameters to be tested

[0069]

[0070] Control Example 1: Effects of different in vitro digestion simulation methods on in vitro digestion curves of starch

[0071] like Figure 3 As shown in Figure 2, the effects of different in vitro digestion simulation methods on the in vitro digestion curve of Doongara rice starch were compared.

[0072] The specific method of scheme 1 (mouth + stomach + intestine) is:

[0073] Compared with the method of Example 1, an oral simulation step is added before gastrointestinal digestion treatment; the specific oral treatment simulation steps are: preparing simulated saliva with a pH of 6.9, wherein the simulated saliva contains a phosphate concentration of 0.1 M and a salivary amylase concentration of 30 U / ml; activating the simulated saliva by water bath to obtain an activated digestive solution, wherein the temperature of the activated water bath is 37° C., the time is 20 min, and the rotation speed is 400 rpm; then adding 2 mL of the activated digestive solution to the rice in step (1), and performing simulated oral digestion for 10 min at a rotation speed of 400 rpm.

[0074] The specific method of scheme 2 (stomach + intestine) is:

[0075] That is, steps (1), (2), (3) of Example 1

[0076] The specific method of scheme 3 (stomach (no enzyme) + intestine) is:

[0077] On the basis of Example 1, pepsin was not added, and other steps and methods were consistent with Example 1.

[0078] The specific method of scheme 4 (intestinal) is:

[0079] On the basis of Example 1, the in vitro simulation of the enzymatic digestion reaction process of the human stomach was omitted (i.e., step (2) was omitted), and the other steps and methods were consistent with those of Example 1.

[0080] from Figure 3 It can be seen that the in vitro digestion curves of Scheme 1 and Scheme 2 are highly overlapped, the digestion rate of Scheme 2 is significantly higher than that of Scheme 3, and the digestion rate of Scheme 3 is significantly higher than that of Scheme 4. This shows that the simulated oral stage has little effect on the digestion of rice, while the gastric acid and pepsin in the simulated gastric digestion stage will significantly promote the in vitro digestion of rice. For this reason, Example 1 of the present invention simplifies the scheme and directly uses the simulated digestion method of stomach + intestine.

[0081] Control Example 2: Comparison of prediction models constructed using different methods of simulating gastrointestinal digestion

[0082] The test method is the same as in Example 1, except that the in vitro digestion simulation method is based on the classic Englyst method.

[0083] (1) In vitro test simulating rice cooking:

[0084] Weigh 200±10 mg of intact rice grains, add 5 glass beads and 50 mg of guar gum powder, and add them to a reagent bottle; add 2.0 mL of distilled water to the reagent bottle and tighten the bottle cap;

[0085] (2) In vitro tests simulate intestinal digestion process:

[0086] The mixed enzyme solution is prepared to consist of 25 mL of sodium acetate buffer and digestive enzymes; the concentration of the sodium acetate buffer is 0.2 M, and the pH is 5.2; the digestive enzymes are composed of pancreatic α-amylase and glucoside amylase, wherein the concentration of the pancreatic α-amylase is 144 U / ml, and the concentration of the glucoside amylase is 15 U / ml; the simulated small intestinal digestive fluid is activated by water bath to obtain an activated digestive fluid, wherein the temperature of the activated water bath is 37° C., the time is 20 min, and the rotation speed is 160 rpm.

[0087] After the simulated small intestinal digestion stage begins, the supernatant is sampled at 0, 10, 20, 30, 60, 90, 120, and 180 min, 200 μL each time, and the sample is quickly transferred to a 2 mL centrifuge tube with a cap to which 800 μL of anhydrous ethanol has been added in advance. The tube is quickly covered with a lid and shaken to inactivate the enzyme, which is used as the test sample solution.

[0088] The results are shown in Table 3. Figure 4 and Figure 5 shown.

[0089] Table 3 and Figure 4 The predicted GI values ​​and clinical rice GI values ​​were demonstrated, and the results showed that the predicted GI values ​​were far from the clinical rice GI values, and there was no discrimination between different samples.

[0090] Table 3 Predicted GI values ​​of rice obtained using the Englyst method

[0091]

[0092] Control Example 3: Effect of Glucosidase Concentration on Prediction Model Accuracy

[0093] On the basis of Example 1, the concentration of glucoside amylase in step (3) was replaced with 5 U / mL at 10 U / mL, and the other steps and parameters were the same as those in Example 1.

[0094] Referring to the method of Example 1, the relationship between the in vitro digestion parameters of standard rice varieties and their predicted GI values ​​was constructed, y = 0.0451x-5.9275 (R 2 =0.5311), where x is AUC-60 and y is the predicted GI value.

[0095] The results are shown in Table 4 and Figure 6 .

[0096] Table 4 Clinical GI values ​​and AUC-60 of rice after changing conditions

[0097]

[0098] The results showed that the GI value predicted by AUC-60 after adjusting the glucoside amylase concentration was far from the clinical GI value, indicating that the glucoside amylase concentration has a great influence on the accuracy of the model.

[0099] The above embodiment is only one implementation of the present invention, and its description is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A method for predicting the glycemic index of rice, characterized in that: The method comprises: performing in vitro digestion simulation on the rice to be predicted, obtaining an in vitro digestion parameter AUC-60, and then substituting the AUC-60 value as x into a model y=0.0548x-134.42 to obtain a y value, wherein the y value is the glycemic index of the rice; Among them, in vitro digestion simulation simulates human stomach digestion and human small intestine digestion, but does not simulate oral digestion; The simulated human gastric digestion is performed by using a simulated gastric fluid of pH 2.0, wherein the simulated gastric fluid is composed of 0.02M-0.03M hydrochloric acid and 2000-3000U / ml pepsin; The small intestinal digestive fluid used to simulate human small intestinal digestion is composed of 0.2M sodium acetate buffer, digestive enzymes, 1-5mM CaC12 and 0.2-1mM MgC12; the digestive enzymes are composed of pancreatic α-amylase and glucosidase, specifically pancreatic α-amylase with a concentration of 1-20U / ml and glucosidase with a concentration of 10U / ml; The in vitro digestion parameter AUC-60 refers to measuring the reducing sugar release at multiple time points within 0-60 min after the start of the enzyme digestion reaction of the rice to be tested in vitro simulating the human small intestine, making a reducing sugar release curve, and converting it into a digestion curve with starch digestibility as the vertical axis and reaction time as the horizontal axis; performing definite integral calculation to obtain the area under the in vitro digestion curve within 0-60 min of the rice to be tested, which is the in vitro digestion parameter AUC-60; In vitro digestion simulation of the predicted rice was performed, including: (1) simulating rice cooking to obtain a rice mixture; (2) In vitro simulation of human stomach enzymatic digestion reaction activity: After cooling the mixed solution obtained in step (1), reacting it with simulated gastric digestive juice to simulate the gastric digestion process of rice in the human body, and terminating the gastric digestion process after reaching the time; (3) In vitro simulation of enzymatic digestion reaction activities of the human small intestine: The mixed solution obtained in step (2) is reacted with simulated small intestinal digestive fluid to simulate the intestinal digestion process of rice in the human body.

2. The method according to claim 1, characterized in that The method for simulating rice cooking in step (1) comprises the following steps: adding rice grains into a glass bottle, wherein the rice varieties to be measured are required to be consistent, the grains have a complete appearance, and there are no gaps as much as possible; adding 3-6 mL of deionized water for every 100-300 mg of rice grains; and boiling the rice grains while avoiding destroying the complete grain structure of the rice or causing the rice to stick to the wall.

3. The method according to claim 1, characterized in that The step (2) of simulating the enzymatic digestion reaction of the human stomach in vitro comprises the following steps: preparing simulated gastric juice with a pH of 2.0; activating the simulated gastric juice by water bath to obtain activated digestive juice, wherein the temperature of the activated water bath is 37° C., the time is 10-20 min, and the rotation speed is 200 rpm-400 rpm; then adding the activated digestive juice to the rice of step (1), performing simulated gastric digestion for 30 min at a rotation speed of 100-200 rpm, and then terminating the gastric digestion.

4. The method according to claim 1, characterized in that The in vitro simulation of the enzymatic digestion reaction activity of the human small intestine in step (3) is performed by using activated simulated small intestinal digestive fluid at 37° C. and 100-200 rpm for 3 hours; wherein the simulated small intestinal digestive fluid contains sodium acetate buffer and digestive enzymes.

5. The method according to claim 4, characterized in that The sodium acetate buffer has a concentration of 0.2M, which is prepared by diluting 2M sodium acetate and 0.2M acetic acid, with a pH of 6.0; the activated simulated small intestinal digestive fluid refers to the simulated small intestinal digestive fluid being treated at 37°C and 200rpm-400rpm for 10-20min.

6. The method according to claim 1, characterized in that The model is constructed by conducting an in vitro digestion simulation experiment on a rice standard with a known GI value, and establishing a functional relationship between the glycemic index GI of the standard sample and the in vitro digestion parameter AUC-60.

7. The method according to claim 6, characterized in that When establishing the model, the in vitro digestion simulation method of claim 1 is used, that is, simulating human gastric digestion and simulating human small intestinal digestion.

8. Application of the method according to any one of claims 1 to 7 in rice variety screening and rice breeding.

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